From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754349Ab3KUSLd (ORCPT ); Thu, 21 Nov 2013 13:11:33 -0500 Received: from terminus.zytor.com ([198.137.202.10]:55229 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751569Ab3KUSLb (ORCPT ); Thu, 21 Nov 2013 13:11:31 -0500 Message-ID: <528E4CBA.8000808@zytor.com> Date: Thu, 21 Nov 2013 10:11:06 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Akinobu Mita CC: LKML , Andrew Morton , Marek Szyprowski , Konrad Rzeszutek Wilk , Thomas Gleixner , Ingo Molnar , x86@kernel.org Subject: Re: [PATCH] x86: enable DMA CMA with swiotlb References: <1384903939-3371-1-git-send-email-akinobu.mita@gmail.com> <528D4A1A.2050100@zytor.com> In-Reply-To: X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/21/2013 07:02 AM, Akinobu Mita wrote: > > I want to use DMA CMA for the feature that requires a single huge chunk > (about 64MB) of host memory. That is tautological. "I want to use the Contiguous Memory Allocator to allocate contiguous memory." > Please refer 3 of 24 in: > http://www.jedec.org/sites/default/files/T_Fujisawa_MF_2013.pdf But yes, it makes sense that a device using host memory would not be able to leverage swiotlb, because the software simply has no clue what the DMA transactions are. In that sense it is fundamentally different from a real IOTLB. -hpa